Provinces and territories are receiving the first doses of H1N1 vaccine this week, just as another round of viral infections is spreading. (CBC)

Canada has officially entered the second wave of the H1N1 flu pandemic, Health Minister Leona Aglukkaq said Friday.

"We are starting to see an increase in the number of people who are getting sick from H1N1," Aglukkaq said in declaring the start of the second wave.

"We've had some deaths this week. It is a serious situation."

The move into the second pandemic phase means that a drop in flu cases won't occur until enough people have been inoculated against the H1N1 influenza A virus — either through vaccination or by contracting the virus, said Dr. David Butler-Jones, Canada's chief public health officer. He spoke to reporters via teleconference.

Health officials in British Columbia, Quebec and the Northwest Territories had already declared the start of a second wave, but this is the first time the same has been done on a national level.

Federal public health officials based their decision on four criteria, Butler-Jones said:

• Number of people testing positive for the virus.
• Reported hospitalizations for flu-like illness.
• More people coming into doctors' offices with flu symptoms.
• Increase in sales of antiviral medications for flu.

Since last week, three more swine flu deaths have been reported in Canada, bringing the total number of fatalities to 86, Aglukkaq told reporters from Yellowknife.

Canadians should rest assured that officials have been responding as if the second wave was already underway, she said.

On Wednesday, Aglukkaq authorized the H1N1 pandemic vaccine for use in Canada for everyone over the age of six months, and the vaccine is in the process of being rolled out in provinces and territories.

Clinical trials worldwide suggest that up to 85 per cent of healthy adults who are immunized will develop immunity within 10 days, Aglukkaq said.

Disease hitting younger people

Aglukkaq encouraged people to talk to their family doctor or public health nurse to get the facts about the vaccine, noting that she will be getting immunized and is recommending the same for her family.

Canada's vaccine order cost about $300 million, Butler-Jones said. Even taking into account the cost of delivering the vaccine, the price pales compared with the cost of not doing anything, he said.

Swine flu remains a disease in which the bulk of illnesses and hospitalizations occur among young people, a common characteristic of pandemic flu viruses.

"This remains largely a young person's disease," said Dr. Thomas Friden, director of the U.S. Centers for Disease Control and Prevention in Atlanta. "But we're seeing it increasingly affect young adults as well as children."

In Canada, the median age of those who have become ill with laboratory-confirmed swine flu is 21, and the median age of those who died is 51, Butler-Jones said. Last week, about half of the people who died of the flu in the U.S. were teenagers.

Ontario has seen more requests for lab testing, more absenteeism in schools and workplaces, and more visits to emergency rooms, the province's chief medical officer of health, Dr. Arlene King, told reporters Friday.

Ontario will first offer the H1N1 vaccine to priority groups who will benefit most, King said. That includes people age 65 and under with chronic health conditions, pregnant women, healthy children between the ages of six months and five years, health-care workers and those living in remote and isolated communities.

Women who are more than 20 weeks into their pregnancy should talk to their doctor about receiving the vaccine that includes an adjuvant, or booster, King said. Healthy women in the first half of their pregnancy may wait to receive the non-adjuvanted form when it becomes available.

The federal government approved the H1N1 vaccine on Wednesday, and King said 722,000 doses of the vaccine will have arrived at the province's 36 local health units by the end of Friday, with a second shipment expected to arrive next week.